we would like to weld 415 martensit

What C level is your material?
You may not be able to use no-PWHT as it could be very brittle in the HAZ.
If the material is normalized (and not Q&T) you might get away with a lot of preheat.
The Ni will help some with this.
There are fillers with Ni in them but be careful.
If the Ni is too high it will lead to retained ferrite, which will later revert to un-tempered martensite.
In Europe I have seen a 410Ni (or 410NiMo).
This will take some serious qualification testing to assure that you have serviceable welds.

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P.E. Metallurgy, consulting work welcomed

Use Inconel filler ERNiCr3 if you cannot carry out what Sir Ed has suggested.

DHURJATI SEN
Kolkata, India